Year	Percent
1991	43.62
1992	41.48
1993	39.38
1994	34.72
1995	34.99
1996	36.84
1997	36.33
1998	34.78
1999	31.27
2000	28.38
2001	27.97
2002	26.95
2003	27.51
2004	26.56
2005	25.76
2006	25.86
2007	27.53
2008	26.17
2009	22.77
2010	20.61
2011	20.03
2012	20.07
2013	20.39
2014	21.69
2015	23.31
2016	25.42
2017	27.15
2018	27.59
2019	24.97